An organic electroluminescence (which may be hereinafter described as an “organic EL”) display device which is one of self-emitting type flat panel display devices is an all solid-state flat panel display device in which organic EL devices are arrayed in a matrix on a substrate such as a glass substrate. In the organic EL display device, anodes and cathodes are formed in stripes, the portions of intersection of which correspond to pixels (organic EL devices). The organic EL devices are externally applied with a voltage of several volts, so that a current flows therethrough. As a result, organic molecules are raised to the excited state. When the organic molecules return to the base state (stable state), they emit an extra energy thereof as a light. The luminescence color is inherent in the organic material.
The organic EL devices are devices self-emitting type and current-driving type. The driving type is classified into a passive matrix type and an active matrix type. The passive matrix type is simple in structure, but has a difficulty in providing full color. On the other hand, the active matrix type can be increased in size, and is also suitable for providing full color, but requires a TFT substrate. For the TFT substrates, a low-temperature polycrystal Si (p-Si), amorphous Si (a-Si), or other TFTs are used.
In the case of the active matrix type organic EL display device, a plurality of TFTs and wires become obstacles, resulting in reduction of the area usable for organic EL pixels. As the driving circuit becomes complicated, and the number of TFTs increases, the effects thereof increase. In recent years, attention has been focused on the method for improving the aperture ratio not by extracting light from a glass substrate, but by adopting a structure in which light is extracted from the top surface side (top emission system).
With the top emission system, for the anode on the bottom surface, ITO: Indium Tin Oxide excellent in hole injection is used. Whereas, for the cathode on the top surface, it is necessary to use a transparent conductive film. However, ITO has a large work function, and is not suitable for electron injection. Further, ITO is deposited with a sputtering method or an ion beam deposition method. This leads to a fear of damage to the electron transport layer (organic material forming organic EL devices) due to plasma ions and secondary electrons during deposition. For this reason, by forming a thin MG layer or copper phthalocyanine layer on the electron transport layer, electron injection is improved, and the damage is avoided.
Partly for the purpose of reflecting light emitted from an organic EL device, the anode for use in such an active matrix type top-emission organic EL display device forms a lamination structure of a transparent oxide conductive film typified by ITO or IZO: Indium Zinc Oxide and a reflective film. For the reflective film herein used, there is often used a metal film with a high reflectivity such as molybdenum-, chromium-, or aluminum-based one (Patent Literature 1), silver-based one (Patent Literature 2), or the like.
Incidentally, the present applicant has heretofore proposed an Ag-based alloy as for a liquid crystal display device (Patent Literature 3), and an Ag-based alloy as for a liquid crystal display device (Patent Literature 4).